New York, New York - Three doses of the Pfizer/BioNTech Covid-19 vaccine appear to neutralize the new Omicron variant, according to preliminary studies.

Pfizer and BioNTech said that two doses of the vaccine showed a significantly reduced effectiveness against Omicron, suggesting people can still get infected with the variant.

However, two jabs are still expected to work against severe disease owing to how the body uses a range of immune cells, including T cells, for protection.

And when it comes to boosters, three doses of the vaccine increased neutralizing antibodies against Omicron in people’s blood 25-fold compared with two doses.

Experts said this showed that booster doses could offer good protection against Omicron.

Laboratory studies showed that the antibody levels reached with three doses of the vaccine were just as good as for two doses against the original Wuhan strain of the virus, which have already been shown to offer high levels of protection.

In a statement, Pfizer and BioNTech said that two doses may still induce protection against severe disease, although people may still get infected.

The companies said the two doses "may not be sufficient to protect against infection with the Omicron variant."

"A more robust protection may be achieved by a third dose, as data from additional studies of the companies indicate that a booster with the current Covid-19 vaccine from Pfizer and BioNTech increases the antibody titers by 25-fold."

"According to the companies’ preliminary data, a third dose provides a similar level of neutralizing antibodies to Omicron as is observed after two doses against wild-type and other variants that emerged before Omicron."

"These antibody levels are associated with high efficacy against both the wild-type virus and these variants."

For the small study on around 20 people, blood samples were obtained from people one month after they received a booster vaccination.

Some samples were from people who had received just two doses three weeks previously.

This latter group had, on average, more than a 25-fold reduction in neutralization titers against the Omicron variant compared with the original Wuhan strain.

The firms said they were continuing to work on a variant-specific vaccine for Omicron and expected to have it available by March "in the event that an adaption is needed to further increase the level and duration of protection."